Effect of Initial Texture on the Evolution of Microstructure and Texture During Rolling of Commercially Pure Titanium at Room and Cryogenic Temperature

Abstract

The evolution of texture and microstructure of commercially pure titanium during unidirectional rolling at room and cryogenic temperature was studied for two different initial orientations, namely RD (rolling direction)-split basal (BA orientation) and prismatic-pyramidal (PP orientation) till 90 pct rolling reduction. Effect of micro-mechanisms of deformation by slip and twinning on texture evolution and grain fragmentation was studied by employing characterization tools like bulk texture measurement using X-ray diffraction and electron back scatter diffraction. Both orientations yield split TD (transverse direction) texture for 90 pct rolling reduction at both the temperatures. Orientation BA showed severe twinning that saturated at deformation of 50 pct followed by slip dominated deformation, while orientation PP showed slip dominated deformation with marginal twinning throughout the rolling reduction at room temperature. Profuse twinning led to homogeneous grain refinement in orientation BA, while orientation PP showed heterogeneous grain refinement due to absence of twinning in some grains at the final stage of deformation. Rolling at cryogenic temperature enhances grain refinement due to extensive twinning that leads to weakening of texture in BA orientation and increase in intensity of texture for PP orientation compared to room temperature rolling. The evolution of microstructure and texture contributed to similar hardness for 90 pct room and cryogenic temperature rolled BA orientation, while 90 pct room temperature rolled PP orientation showed lower hardness.